The 2008 Memorial Day Weekend tornado outbreak will continue to hammer the U.S. today, even as residents from Iowa and Minnesota clean up from the devastating tornadoes that killed eight people Sunday afternoon. A mile-wide tornado plowed through Parkersburg, Iowa between 5pm and 6pm CDT yesterday, killing five people in that city, and two in nearby New Hartford. It was the deadliest tornado in Iowa in more than 40 years. The tornado passed just north of the airport in Waterloo, Iowa, which recorded sustained winds of 64mph, gusting to 94 mph at 5:37pm CDT. Damage appeared to be at least EF-4 in photos I saw, and possibly EF-5 (over 200 mph). In Minnesota, another powerful twister killed at least one person and injured 9 in the Minneapolis suburb of Hugo.

Figure 1. Satellite image of the supercell thunderstorms that spawned the Parkerburg, Iowa and Hugo, Minnesota tornadoes on May 25, 2008.

The slow-moving low pressure system responsible for all the mayhem began in Colorado on Thursday, when the Storm Prediction Center (SPC) recorded 48 reports of tornadoes, including the EF-3 mile-wide twister that killed one person in Windsor, Colorado. On Friday, an additional 63 tornado reports occurred, mostly in Kansas. The tornado that hit Quinter, Kansas on Friday was the eighth violent EF-4 tornado of the year. Also on Friday, two people were killed in Cairo, Kansas when a tornado smashed a car trying to flee the storm. If you want to see why one should not try to escape a tornado in a car, take a look at what the tornado did to the car. Saturday was relatively quiet, with only 13 tornado reports, but Sunday's tally of 43 brought the 4-day total from the 2008 Memorial Day weekend outbreak to a remarkable 157 tornado reports. Some of these tornado reports are undoubtedly of the same tornado, so the actual number of tornadoes for the 4-day outbreak may be less than 150. BBC has some awesome aerial footage of the weekend tornadoes.

Figure 2. Radar reflectivity image (top) of the May 25, 2008 Parkersburg, Iowa tornado. The position of Parkersburg is marked by a circle with a cross in the middle. Bottom: Doppler velocity image of the tornado, showing a small core of red and blue colors right next to each other, denoting strong winds towards and away from the radar, the classic signature of a tornado vortex.

Figure 3. Radar reflectivity image (top) of the May 25, 2008 Hugo, Minnesota tornado. The position of Hugo is marked by a circle with a cross in the middle. Bottom: Doppler velocity image of the tornado, showing a small core of red and blue colors right next to each other, denoting strong winds towards and away from the radar, the classic signature of a tornado vortex. We've also saved a 12-frame radar animation of the Hugo cell, thanks to wunderground member Todd S.

Tallying up the numbersThe death toll from Sunday pushes this year's tornado deaths to 111, the most since 1998, when 130 were recorded. Assuming that the Parkersburg, Iowa tornado was an EF-4 or EF-5, there have been nine violent EF-4 or EF-5 tornadoes this year. This is the most since 1999, when 13 such twisters were recorded. The total number of tornadoes this year is approaching 1100, and we may challenge the all time record for tornadoes in a year of 1817, set in 2004. Could this be a sign of climate change? No, I don't think so, and I'll explain why in a blog later this week.

Severe weather forecastSevere weather will pound the U.S. again this Memorial Day, with the main action expected to stretch more than halfway across the country--from Texas to New York. NOAA's Storm Prediction Center has placed much of Kansas, Oklahoma, and the Texas Panhandle under its "Moderate Risk" category for severe weather, one step below its highest level of concern, "High Risk". Yesterday was also a "Moderate Risk" day in Iowa and Minnesota. The Weather Underground Severe Weather page and Tornado page are good places to go to follow the severe weather. Also, tune in to the chase accounts and awesome storm photos from Wunderblogger Mike Theiss. After today, it appears the severe weather outbreak will finally diminish, with only a slight risk of severe weather expected Tuesday, and no severe weather expected Wednesday.

Possible development in the Western Caribbean or Eastern Pacific late this weekFor the past 3-6 days, our most reliable global computer weather forecast models have been predicting the development of a low pressure system near or over Central America by Friday of this week. Given the persistence in the models in developing this low, we need to be alert to the possibility of a tropical depression forming in either the Western Caribbean or Eastern Pacific, on either side of Costa Rica and Nicaragua. It is uncertain which ocean basin such a storm might form in, and whether or not there will be a tropical wave around to help kick off development. It may be that the low pressure region will stay anchored over land south of the Yucatan Peninsula, preventing any development. This is the solution preferred by the ECMWF model in its last few runs. However, the GFS, NOGAPS, and Canadian models all predict a tropical depression might form in the Western Caribbean near Mexico's Yucatan Peninsula. In contrast, the UKMET shows development in the Eastern Pacific, on the Pacific side of Central America. Climatologically, May tropical storms are much more common in the Eastern Pacific than the Western Caribbean, so we should not discount the UKMET solution, even though it is an outlier. All five models predict that the Central American low pressure area will move northward towards the Gulf of Mexico, and wind shear may fall enough to allow a tropical depression to form should the low's center emerge over water. I'll be posting daily updates on the situation this week.

These are pictures taken of the storm that went through Forest Lake / Hugo, MN. The tornado passed 3 miles south of us, but we got a pretty vicious shot of hail for about 15 minutes straight. The pictures of bldg damage are west of the worst tornado damage, probably where the funnel cloud was just about to reach the ground.

CC, as long as there is something trying to get it's act together in the E-Pac, the NW Caribbean will be quiet. In order for something to develop in the w. Caribbean, the E-Pac system will have to develop and move westward fairly quickly or dissipate completely. E-Pac wins almost always if there are competing systems in that area this time of year.

156. FLWeatherFreak91 3:54 PM GMT on May 26, 2008 152. Drakoen 11:52 AM EDT on May 26, 2008 Hide this comment.lol the GFS 12z thinks it will cross over Panama. That is a big difference from the previous runs.

This could allow for a circulation established in the Pacific to remain stronger upon emergence into the Caribbean.

Yes and that would allow the system more time over water. This is more inline with the NOGAPS.

Since this is originating in the E-pac I took a look at the geography of central America to determine how it will affect the circulation, and also to examine the flooding potential in these areas.

Mountains of Northern Panama- 1500-2200 ft.

Costa Rica- plains in the North, mountains approaching 8000 ft in the South

Nicaragua- plains in the South and mountains approaching 4000 ft in the North.

Honduras- Mountainous, approaching 5000 ft

Guatemala- Very mountainous with peaks surpassing 9000 ft.

If a circulation does form in the Pacific and moves ashore in any of these countries massive flooding may occur. It seems to me that most organized systems in the E-pac usually move AWAY from the coast and not toward it...

At this time, the Tropical Atlantic remains quiet, but the environmental conditions are starting to change throughout the basin and becoming more favorable for tropical development, especially off Africa. But right now, my main focus remains on the computer models forecasting a developing tropical system in the Northwest Caribbean in the coming week.

Now, there are six main computer models that are watched for tropical development. At this time, we now have three models all depicting a developing tropical storm in the Northwest Caribbean by Thursday or Friday. There are two models (UKMET and ECMWF) that do not show this, although the UKMET (United Kingdom Meteorological model) shows a rather strong tropical storm off the Mexican coast. The last model, the NAM (North American Model) is not known for tropical storm forecasting and does not go that far out in time, so we cannot take this model into account.

Referring to the models depicting a developing tropical storm in the Northwest Caribbean by late week, this seems quite reasonable and, in fact, I'm now confident in forecasting a tropical storm in the Northwest Caribbean by Friday. Where the system goes from there still remains quite cloudy (no pun intended), but all three models show the storm strengthening into a hurricane and hitting somewhere in Central or Southern Florida. This is the highest model consensus that I have seen to date. But, the most important thing to note is the fact that this storm has not even developed yet and it still remains at least a week away from happening, so much can change during this time.

Putting this computer storm, we do have two very impressive tropical waves over Africa and about ready to come out into the Atlantic. It seems that the second tropical wave could have some potential for development, but it remains unlikely as it is not climatologically favorable to occur.

For now, no tropical development is expected within the next 24 to 48 hours, but there could be some tropical development occuring in the Northwest Caribbean within three to five days. Stay tuned for further updates.

hey everyone, i really hope this storm doesn't be a cat4 or cat5, cuz it looks like it going to make a second landfall in SC which could be cooll..But i updated my blog, go and leave some comments for me!

weather makes waves in the gomex.....for thelast 10 days groundswell from the Yucatan has been sending us waves Srq/tampa/St.Pete., As was explained to me, a gradient set up near Cuba, winds blew 20-30 through the channel funneling swell into the Gomex. It was dreamlike long period groundswell - I am so exhausted, my arms are like pasta between all this surf and grooming horses at work.

Among surfers this is considered a very RARE occurrence.

Please feel free to correct any of the above if I got the weather stuff wrong.

The total number of tornadoes this year is approaching 1100, and we may challenge the all time record for tornadoes in a year of 1817, set in 2004~ I've seen alot of 2004 climotoligy comparisions this year.

You can view here and see how at 120hrs upper level conditions might become more favorable for development of a TD/TS in the SW/NW caribbean next week.Nothing is expected over the next day or two so we'll see were we are at come mid week.

CMC at maximum range (overdeveloping it, obviously) is developing a strong Cat 2 or weak Cat 3. Note that this pretty much means nothing, as the CMC has a tendency to ignore environmental conditions and overdevelop tropical cyclones (what matters more is where it develops them):

"For the most part...Friday and into the weekend should remain ratherdry. There will be a small possibility for some isolated afternoonactivity but this should be rather isolated. Overall have remainedrather close to gui for probability of precipitation for Friday and through the weekend.Another weak shortwave is expected to move to the north of the areafor the late weekend...which will bring small rain chances to thearea for Sunday into Monday as a weak boundary moves through theregion. .......

Cimss 850mb vorticity and Cimss 700-850Hpa Layer suggests a broad area of low pressure is developing west of Nicaragua. This is also reinforced with GFS, CMC, and NOGAPS 850mb vorticity. Water vapor imagery is showing moisture advecting east into Central America and the Caribbean. This moisture may also be enhance by the westerly flow from a surface cold front extending down in eastern Cuba and Jamaica.

If we know how cracked out the CMC is then why do we even bother paying attention to what it says is going to happen...however if it keeps spitting out these crazy fantasy storms its going to be right eventually.

112. weathersp 10:19 AM CDT on May 26, 2008 13. MasterForecaster 10:17 AM EDT on May 26, 2008Well let's see how many comments this blog can go without a fight. My guess is 112. We make it past 112 without a fight an I'll buy a round for everyone lol

"For the most part...Friday and into the weekend should remain rather dry. There will be a small possibility for some isolated afternoon activity but this should be rather isolated. Overall have remained rather close to gui for probability of precipitation for Friday and through the weekend. Another weak shortwave is expected to move to the north of the area for the late weekend...which will bring small rain chances to the area for Sunday into Monday as a weak boundary moves through the region. .......

13. MasterForecaster 10:17 AM EDT on May 26, 2008 Well let's see how many comments this blog can go without a fight. My guess is 112. We make it past 112 without a fight an I'll buy a round for everyone lol